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.TH SYSTEM 3C "Dec 14, 2006"
.SH NAME
system \- issue a shell command
.SH SYNOPSIS
.LP
.nf
#include <stdlib.h>

\fBint\fR \fBsystem\fR(\fBconst char *\fR\fIstring\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBsystem()\fR function causes \fIstring\fR to be given to the shell as
input, as if \fIstring\fR had been typed as a command at a terminal. The
invoker waits until the shell has completed, then returns the exit status of
the shell in the format specified by \fBwaitpid\fR(3C).
.sp
.LP
If \fIstring\fR is a null pointer, \fBsystem()\fR checks if the shell exists
and is executable.  If the shell is available, \fBsystem()\fR returns a
non-zero value; otherwise, it returns \fB0\fR.
.sp
.LP
The \fBsystem()\fR function sets the \fBSIGINT\fR and \fBSIGQUIT\fR signals to
be ignored, and blocks the \fBSIGCHLD\fR signal for the calling thread, while
waiting for the command to terminate. The \fBsystem()\fR function does not
affect the termination status of any child of the calling processes other than
the process it creates.
.sp
.LP
The termination status of the process created by the \fBsystem()\fR function is
not affected by the actions of other threads in the calling process (it is
invisible to \fBwait\fR(3C)) or by the disposition of the \fBSIGCHLD\fR signal
in the calling process, even if it is set to be ignored. No \fBSIGCHLD\fR
signal is sent to the process containing the calling thread when the command
terminates.
.SH RETURN VALUES
.sp
.LP
The \fBsystem()\fR function executes \fBposix_spawn\fR(3C) to create a child
process running the shell that in turn executes the commands in \fIstring\fR.
If \fBposix_spawn()\fR fails, \fBsystem()\fR returns \fB\(mi1\fR and sets
\fBerrno\fR to indicate the error; otherwise the exit status of the shell is
returned.
.SH ERRORS
.sp
.LP
The \fBsystem()\fR function may set \fBerrno\fR values as described by
\fBfork\fR(2), in particular:
.sp
.ne 2
.na
\fB\fBEAGAIN\fR\fR
.ad
.RS 10n
A resource control or  limit on the total number of  processes, tasks or LWPs
under execution by a single user,  task,  project, or  zone has been exceeded,
or the total amount of system memory available  is temporarily insufficient to
duplicate this process.
.RE

.sp
.ne 2
.na
\fB\fBENOMEM\fR\fR
.ad
.RS 10n
There is not enough swap space.
.RE

.sp
.ne 2
.na
\fB\fBEPERM\fR\fR
.ad
.RS 10n
The  {\fBPRIV_PROC_FORK\fR} privilege is  not asserted in the effective set of
the calling process.
.RE

.SH USAGE
.sp
.LP
The \fBsystem()\fR function manipulates the signal handlers for \fBSIGINT\fR
and \fBSIGQUIT\fR. It is therefore not safe to call \fBsystem()\fR in a
multithreaded process, since some other thread that manipulates these signal
handlers and a thread that concurrently calls \fBsystem()\fR can interfere with
each other in a destructive manner.  If, however, no such other thread is
active, \fBsystem()\fR can safely be called concurrently from multiple threads.
See \fBpopen\fR(3C) for an alternative to \fBsystem()\fR that is thread-safe.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	Unsafe
.TE

.SH SEE ALSO
.sp
.LP
.BR ksh (1),
.BR sh (1),
.BR popen (3C),
.BR posix_spawn (3C),
.BR wait (3C),
.BR waitpid (3C),
.BR attributes (7),
.BR standards (7)
